JavaScript Object Methods — JavaScript interactive lesson

What are Object Methods?

Methods are actions that can be performed on objects.

Methods are functions stored as property values .

Example

const
person = {
  firstName: "John", lastName: "Doe", age: 50, fullName: function() {
    return this .firstName + " " + this .lastName;
  }
};

Property	Value
firstName	John
lastName	Doe
age	50
fullName	function() { return this.firstName + " " + this.lastName; }

The this Keyword

In an object method, this refers to the object.

Example 1

const person = {
  firstName: "John", lastName: "Doe", id: 5566, getId: function() {
    return this .id;
  }
};
let number = person.getId();

In the example above, this refers to the person object .

this.id means the id property of the person object .

Example 2

const
person = {
  firstName: "John", lastName: "Doe", age: 50, fullName: function() {
    return this .firstName + " " + this .lastName;
  }
};

In the example above, this refers to the person object .

this.firstName means the firstName property of the person object .

this.lastName means the lastName property of the person object .

Accessing Object Methods

To call an object method, add parentheses () :

Without parentheses you get the function itself.

Syntax

objectName.methodName
()

If you call a method with parentheses , it will execute as a function :

name = person.fullName();

If you call a method without parentheses , it will return the function definition :

name = person.fullName;

Adding a Method to an Object

You can add a method to an object by assigning a function to a property :

Example

// Assign person.name to a function person.name = function () {
return this.firstName + " " + this.lastName;
};

In the example above, person.name is a property with a function assigned to it.

Adding a JavaScript Method

This example uses the JavaScript toUpperCase() method to convert a text to uppercase:

person.name = function () {
 return (this.firstName + " " + this.lastName).toUpperCase();
};

Summary

Methods are functions stored as object properties
Call a method with parentheses: person.fullName()
In methods, this refers to the object
You can add methods to objects by assigning a function to a property

What are Object Methods?

Methods are actions that can be performed on objects.

Methods are functions stored as property values .

Example

const
person = {
  firstName: "John", lastName: "Doe", age: 50, fullName: function() {
    return this .firstName + " " + this .lastName;
  }
};

Property	Value
firstName	John
lastName	Doe
age	50
fullName	function() { return this.firstName + " " + this.lastName; }

The this Keyword

In an object method, this refers to the object.

Example 1

const person = {
  firstName: "John", lastName: "Doe", id: 5566, getId: function() {
    return this .id;
  }
};
let number = person.getId();

In the example above, this refers to the person object .

this.id means the id property of the person object .

Example 2

const
person = {
  firstName: "John", lastName: "Doe", age: 50, fullName: function() {
    return this .firstName + " " + this .lastName;
  }
};

In the example above, this refers to the person object .

this.firstName means the firstName property of the person object .

this.lastName means the lastName property of the person object .

Accessing Object Methods

To call an object method, add parentheses () :

Without parentheses you get the function itself.

Syntax

objectName.methodName
()

If you call a method with parentheses , it will execute as a function :

name = person.fullName();

If you call a method without parentheses , it will return the function definition :

name = person.fullName;

Adding a Method to an Object

You can add a method to an object by assigning a function to a property :

Example

// Assign person.name to a function person.name = function () {
return this.firstName + " " + this.lastName;
};

In the example above, person.name is a property with a function assigned to it.

Adding a JavaScript Method

This example uses the JavaScript toUpperCase() method to convert a text to uppercase:

person.name = function () {
 return (this.firstName + " " + this.lastName).toUpperCase();
};

Summary

Methods are functions stored as object properties
Call a method with parentheses: person.fullName()
In methods, this refers to the object
You can add methods to objects by assigning a function to a property